How is the case-fatality rate defined?

• A. The number of people who die from the disease within a certain period divided by the total number of people who have the disease.
• B. The number of deaths in the general population per year.
• C. The proportion of patients who recover within a year.
• D. The incidence rate of the disease.

Answer: (A)

Case-fatality rate measures how deadly a disease is among those who have been diagnosed. It is calculated by taking the number of deaths from the disease during a defined time period and dividing by the total number of diagnosed cases of the disease in that same period. The result expresses the proportion of cases that die from the disease. This is different from the overall mortality rate, which looks at deaths in the entire population regardless of disease, and from incidence, which counts new cases arising. It’s also not the proportion who recover—that would be a recovery proportion. For example, if 100 people are diagnosed with a disease in a month and 5 die during that month, the case-fatality rate is 5%. Remember, CFR can be affected by how completely cases are detected and by the care available.